Suspension, the HPA Axis and Resistance to Infection

Space flight alters the body's defense against infections and tumors. Dr. Gerald Sonnenfeld is exploring these changes in immune response in two ways: to see if space flight conditions can actually increase the body's ability to withstand infections and whether spaceflight-induced stress can cause these changes in the immune system.

Principal Investigator:

Gerald Sonnenfeld, Ph.D.

Organization:

Morehouse School of Medicine

Project Ended:

2004

This project was designed to determine the effects of space flight conditions expressed in the hindlimb unloading model for rodents on resistance to infection. Additionally, the role of the neuroendocrine system in regulating resistance to infection in this system was to be determined.

We have been able to show that hindlimb-unloaded mice had decreased resistance to infection with gram negative bacteria then did control mice. We were also able to show that pretreatment with Active Hexose Correlated Compound (AHCC), a nutritional supplement, protected mice from infection. The AHCC appeared to act by enhancing immune responses in the hindlimb-unloaded mice. The same bacteria were shown to have enhanced growth in the presence of catecholamines, which suggested that the stress response occurring in the hindlimb unloaded mice could contribute to the decreased resistance to infection observed.

The specific aims of the study were:

To expand the range of infections altered by AOH suspension. We had already shown that resistance to some infections that are not likely to be risks during space flight was altered by AOH suspension. We now determined that infections that could be a risk during space flight are affected by the suspension model.

To determine the mechanism of alteration of resistance to infection induced by AOH suspension. Although previous studies had shown that immune responses are altered by space flight, we now extended these studies to determine the role of the neuroendocrine system in regulating infections. This was carried out using two approaches. The data obtained from experiments using both approaches was integrated to allow for development of a model for the mechanism(s) of the effects of hindlimb suspension on resistance to infections.

Principal Investigator:

Gerald Sonnenfeld, Ph.D.

Organization:

Morehouse School of Medicine

Project Ended:

2004

Our development of AHCC as a potential countermeasure for immune dysfunction induced by space flight has led to a new grant from the Amino Up Chemical Company to study the use of AHCC to prevent infection during severe trauma.